C# NotifyProperty未触发_C#_Xaml_Xamarin

C# NotifyProperty未触发

c# xaml xamarin

C# NotifyProperty未触发,c#,xaml,xamarin,C#,Xaml,Xamarin,我在同一页上有两个按钮，一个在我的图库下方，另一个在底部导航栏中。两个命令都会触发，但底部的命令已被破坏。它永远不会去我的房间 <Label Grid.Row="0" Grid.Column="0" Text="IMAGES" XAlign="Start" YAlign="Center" Style="{StaticResource Labelfont}" TextColor="White"/> <Grid x:Name="ImageGall

我在同一页上有两个按钮，一个在我的图库下方，另一个在底部导航栏中。两个命令都会触发，但底部的命令已被破坏。它永远不会去我的房间

  <Label Grid.Row="0" Grid.Column="0" Text="IMAGES" XAlign="Start" YAlign="Center" Style="{StaticResource Labelfont}" TextColor="White"/>
                <Grid x:Name="ImageGallerys">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*">
                        </RowDefinition>
                        <RowDefinition Height="128">
                        </RowDefinition>
                        <RowDefinition Height="Auto">
                        </RowDefinition>
                    </Grid.RowDefinitions>
                    <Image 
                        Source="{Binding PreviewImage}" Grid.Row="0">
                    </Image>
                    <custom:ImageGallery ItemsSource="{Binding Images}" Grid.Row="1">
                        <custom:ImageGallery.ItemTemplate>
                            <DataTemplate>
                                <Image Source="{Binding Source}" Aspect="AspectFit">
                                    <Image.GestureRecognizers>
                                        <TapGestureRecognizer Command="{Binding Path=BindingContext.PreviewImageCommand, Source={x:Reference EditIssue}}" CommandParameter="{Binding ImageId}" />
                                    </Image.GestureRecognizers>
                                </Image>
                            </DataTemplate>
                        </custom:ImageGallery.ItemTemplate>
                    </custom:ImageGallery>
                    <Button 
                        Grid.Row="2" Text="Photo" Command="{Binding CameraCommand}">
                    </Button>
                    <Button 
                        Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                    </Button>
                </Grid>



<!--Bottom Navigation Bar-->
        <Grid Grid.Row="2">
            <Grid.RowDefinitions>
                <RowDefinition Height="*" />
                <RowDefinition Height="50" />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="20" />
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="20" />
            </Grid.ColumnDefinitions>
        <StackLayout x:Name="slButtons" Grid.ColumnSpan="3" Grid.Row="1" Orientation="Horizontal" HorizontalOptions="FillAndExpand" Spacing="5" BackgroundColor="White">
            <StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand"  BackgroundColor="#FBB040">
                <Button 
                    Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                </Button>
            </StackLayout>

这是应该调用NotifyProperty之前的方法

  <Label Grid.Row="0" Grid.Column="0" Text="IMAGES" XAlign="Start" YAlign="Center" Style="{StaticResource Labelfont}" TextColor="White"/>
                <Grid x:Name="ImageGallerys">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*">
                        </RowDefinition>
                        <RowDefinition Height="128">
                        </RowDefinition>
                        <RowDefinition Height="Auto">
                        </RowDefinition>
                    </Grid.RowDefinitions>
                    <Image 
                        Source="{Binding PreviewImage}" Grid.Row="0">
                    </Image>
                    <custom:ImageGallery ItemsSource="{Binding Images}" Grid.Row="1">
                        <custom:ImageGallery.ItemTemplate>
                            <DataTemplate>
                                <Image Source="{Binding Source}" Aspect="AspectFit">
                                    <Image.GestureRecognizers>
                                        <TapGestureRecognizer Command="{Binding Path=BindingContext.PreviewImageCommand, Source={x:Reference EditIssue}}" CommandParameter="{Binding ImageId}" />
                                    </Image.GestureRecognizers>
                                </Image>
                            </DataTemplate>
                        </custom:ImageGallery.ItemTemplate>
                    </custom:ImageGallery>
                    <Button 
                        Grid.Row="2" Text="Photo" Command="{Binding CameraCommand}">
                    </Button>
                    <Button 
                        Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                    </Button>
                </Grid>



<!--Bottom Navigation Bar-->
        <Grid Grid.Row="2">
            <Grid.RowDefinitions>
                <RowDefinition Height="*" />
                <RowDefinition Height="50" />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="20" />
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="20" />
            </Grid.ColumnDefinitions>
        <StackLayout x:Name="slButtons" Grid.ColumnSpan="3" Grid.Row="1" Orientation="Horizontal" HorizontalOptions="FillAndExpand" Spacing="5" BackgroundColor="White">
            <StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand"  BackgroundColor="#FBB040">
                <Button 
                    Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                </Button>
            </StackLayout>

public async Task ExecutePickCommand()
        {
            var file = await CrossMedia.Current.PickPhotoAsync();

            if (file == null)
                return;

            byte[] imageAsBytes = null;
            using (var memoryStream = new MemoryStream())
            {
                file.GetStream().CopyTo(memoryStream);
                file.Dispose();
                imageAsBytes = memoryStream.ToArray();
            }

            if (imageAsBytes.Length > 0)
            {
                var resizer = DependencyService.Get<IImageResize>();
                imageAsBytes = resizer.ResizeImage(imageAsBytes, 1080, 1080);

                var imageSource = ImageSource.FromStream(() => new MemoryStream(imageAsBytes));
                _images.Add(new GalleryImage { Source = imageSource, OrgImage = imageAsBytes });
            }
        }

public异步任务ExecutePickCommand（）
{
var file=await CrossMedia.Current.PickPhotoAsync（）；
if（file==null）
返回；
字节[]imageAsBytes=null；
使用（var memoryStream=new memoryStream（））
{
file.GetStream（）.CopyTo（memoryStream）；
Dispose（）；
imageAsBytes=memoryStream.ToArray（）；
}
如果（imageAsBytes.Length>0）
{
var resizer=DependencyService.Get（）；
imageAsBytes=resizer.ResizeImage（imageAsBytes，10801080）；
var imageSource=imageSource.FromStream（（）=>newmemoryStream（imageAsBytes））；
_Add（新的GalleryImage{Source=imageSource，OrgImage=imageAsBytes}）；
}
}

这是Notifypropery部分，它应该进入方法ItemSourceChange，就像它在我的第一个按钮中所做的一样，在第二个按钮之后它就结束了

  <Label Grid.Row="0" Grid.Column="0" Text="IMAGES" XAlign="Start" YAlign="Center" Style="{StaticResource Labelfont}" TextColor="White"/>
                <Grid x:Name="ImageGallerys">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*">
                        </RowDefinition>
                        <RowDefinition Height="128">
                        </RowDefinition>
                        <RowDefinition Height="Auto">
                        </RowDefinition>
                    </Grid.RowDefinitions>
                    <Image 
                        Source="{Binding PreviewImage}" Grid.Row="0">
                    </Image>
                    <custom:ImageGallery ItemsSource="{Binding Images}" Grid.Row="1">
                        <custom:ImageGallery.ItemTemplate>
                            <DataTemplate>
                                <Image Source="{Binding Source}" Aspect="AspectFit">
                                    <Image.GestureRecognizers>
                                        <TapGestureRecognizer Command="{Binding Path=BindingContext.PreviewImageCommand, Source={x:Reference EditIssue}}" CommandParameter="{Binding ImageId}" />
                                    </Image.GestureRecognizers>
                                </Image>
                            </DataTemplate>
                        </custom:ImageGallery.ItemTemplate>
                    </custom:ImageGallery>
                    <Button 
                        Grid.Row="2" Text="Photo" Command="{Binding CameraCommand}">
                    </Button>
                    <Button 
                        Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                    </Button>
                </Grid>



<!--Bottom Navigation Bar-->
        <Grid Grid.Row="2">
            <Grid.RowDefinitions>
                <RowDefinition Height="*" />
                <RowDefinition Height="50" />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="20" />
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="20" />
            </Grid.ColumnDefinitions>
        <StackLayout x:Name="slButtons" Grid.ColumnSpan="3" Grid.Row="1" Orientation="Horizontal" HorizontalOptions="FillAndExpand" Spacing="5" BackgroundColor="White">
            <StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand"  BackgroundColor="#FBB040">
                <Button 
                    Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                </Button>
            </StackLayout>

 public static readonly BindableProperty ItemsSourceProperty =
            BindableProperty.Create<ImageGallery, IList>(
                view => view.ItemsSource,
                default(IList),
                BindingMode.TwoWay,
                propertyChanging: (bindableObject, oldValue, newValue) => {
                    ((ImageGallery)bindableObject).ItemsSourceChanging();
                },
                propertyChanged: (bindableObject, oldValue, newValue) => {
                    ((ImageGallery)bindableObject).ItemsSourceChanged(bindableObject, oldValue, newValue);
                }
            );

        public IList ItemsSource
        {
            get
            {
                return (IList)GetValue(ItemsSourceProperty);
            }
            set
            {

                SetValue(ItemsSourceProperty, value);
            }
        }

        void ItemsSourceChanging()
        {
            if (ItemsSource == null)
                return;
        }


        void ItemsSourceChanged(BindableObject bindable, IList oldValue, IList newValue)
        {
            if (ItemsSource == null)
                return;

            var notifyCollection = newValue as INotifyCollectionChanged;
            if (notifyCollection != null)
            {
                notifyCollection.CollectionChanged += (sender, args) => {
                    if (args.NewItems != null)
                    {
                        if (args.NewItems.Count > 0)
                        {
                            foreach (var newItem in args.NewItems)
                            {
                                var view = (View)ItemTemplate.CreateContent();
                                var bindableObject = view as BindableObject;
                                if (bindableObject != null)
                                    bindableObject.BindingContext = newItem;
                                _imageStack.Children.Add(view);
                            }
                        }
                    }
                    else
                    {
                        _imageStack.Children.Clear();
                        foreach (var Item in ItemsSource)
                        {
                            var view = (View)ItemTemplate.CreateContent();
                            var bindableObject = view as BindableObject;
                            if (bindableObject != null)
                                bindableObject.BindingContext = Item;
                            _imageStack.Children.Add(view);
                        }
                    }
                    if (args.OldItems != null)
                    {
                        // not supported
                    }
                };

公共静态只读BindableProperty项资源属性=
BindableProperty.Create(
view=>view.ItemsSource，
违约（IList），
BindingMode.TwoWay，
属性更改：（bindableObject、oldValue、newValue）=>{
（（ImageGallery）bindableObject.ItemsSourceChange（）；
},
propertyChanged：（bindableObject、oldValue、newValue）=>{
（（ImageGallery）bindableObject）.ItemsSourceChanged（bindableObject，oldValue，newValue）；
}
);
公共IList项目资源
{
得到
{
返回（IList）GetValue（ItemsSourceProperty）；
}
设置
{
设置值（ItemsSourceProperty，value）；
}
}
作废项目采购更改（）
{
if（ItemsSource==null）
返回；
}
void ItemsSourceChanged（BindableObject bindable、IList oldValue、IList newValue）
{
if（ItemsSource==null）
返回；
var notifyCollection=INOTIFYCOLLECTION更改时的新值；
if（notifyCollection！=null）
{
notifyCollection.CollectionChanged+=（发件人，参数）=>{
如果（args.NewItems！=null）
{
如果（args.NewItems.Count>0）
{
foreach（args.NewItems中的var newItem）
{
var view=（view）ItemTemplate.CreateContent（）；
var bindableObject=作为bindableObject查看；
if（bindableObject！=null）
bindableObject.BindingContext=newItem；
_imageStack.Children.Add（视图）；
}
}
}
其他的
{
_imageStack.Children.Clear（）；
foreach（ItemsSource中的var项）
{
var view=（view）ItemTemplate.CreateContent（）；
var bindableObject=作为bindableObject查看；
if（bindableObject！=null）
bindableObject.BindingContext=项；
_imageStack.Children.Add（视图）；
}
}
如果（args.OldItems！=null）
{
//不支持
}
};

我发现如果我这样做了，它最终会像上面的按钮一样调用notifyproperty。但是现在由于这个按钮中的nullreference错误，它崩溃了，因为它似乎创建了另一个实例或其他什么

  <Label Grid.Row="0" Grid.Column="0" Text="IMAGES" XAlign="Start" YAlign="Center" Style="{StaticResource Labelfont}" TextColor="White"/>
                <Grid x:Name="ImageGallerys">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*">
                        </RowDefinition>
                        <RowDefinition Height="128">
                        </RowDefinition>
                        <RowDefinition Height="Auto">
                        </RowDefinition>
                    </Grid.RowDefinitions>
                    <Image 
                        Source="{Binding PreviewImage}" Grid.Row="0">
                    </Image>
                    <custom:ImageGallery ItemsSource="{Binding Images}" Grid.Row="1">
                        <custom:ImageGallery.ItemTemplate>
                            <DataTemplate>
                                <Image Source="{Binding Source}" Aspect="AspectFit">
                                    <Image.GestureRecognizers>
                                        <TapGestureRecognizer Command="{Binding Path=BindingContext.PreviewImageCommand, Source={x:Reference EditIssue}}" CommandParameter="{Binding ImageId}" />
                                    </Image.GestureRecognizers>
                                </Image>
                            </DataTemplate>
                        </custom:ImageGallery.ItemTemplate>
                    </custom:ImageGallery>
                    <Button 
                        Grid.Row="2" Text="Photo" Command="{Binding CameraCommand}">
                    </Button>
                    <Button 
                        Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                    </Button>
                </Grid>



<!--Bottom Navigation Bar-->
        <Grid Grid.Row="2">
            <Grid.RowDefinitions>
                <RowDefinition Height="*" />
                <RowDefinition Height="50" />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="20" />
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="20" />
            </Grid.ColumnDefinitions>
        <StackLayout x:Name="slButtons" Grid.ColumnSpan="3" Grid.Row="1" Orientation="Horizontal" HorizontalOptions="FillAndExpand" Spacing="5" BackgroundColor="White">
            <StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand"  BackgroundColor="#FBB040">
                <Button 
                    Grid.Row="2" Text="Pick" Command="{Binding PickCommand}">
                </Button>
            </StackLayout>

<custom:ImageGallery ItemsSource="{Binding Images}" Grid.Row="1" x:Name="ImageGalleryss">
                        <Button 
                        Grid.Row="3" Text="Pick" Command="{Binding PickCommand}">
                        </Button>
                </custom:ImageGallery>

是

\u images

一个

可观察到的采集

是“可观察到的采集”\u images=新的可观察到的采集（）奇怪的是，它与本地网格中的按钮一起工作，但底部导航栏中的按钮会触发，但notifyproperty在本地网格之外的任何地方都不起作用，所以可能需要自定义库？